Muldrotha, the Gravetide, Timestream Navigator, and Riptide Shapeshifter

Prerequisites

• Muldrotha, the Gravetide on the battlefield
• Timestream Navigator on the battlefield
• Riptide Shapeshifter on the battlefield
• undefined the first turn, with plus six available each extra turn available

Steps

1. Activate Timstream Navigator by paying , tapping it and putting it on the bottom of your library, causing you to take an extra turn after this one
2. Activate Riptide Shapeshifter by paying and sacrificing it, naming any of Timestream Navigator's types, and then revealing Timestream Navigator from your library and putting it onto the battlefield
3. Move to your next turn
4. Cast Riptide Shapeshifter from your graveyard by paying
5. Repeat

Results

• Infinite turns